Bow saw



Sept. 8, 1953 Filed May 11, 1951 2 Shets-Sheet l J. E. HAMMARSTRGM 2,651,341

BOW SAW Sept. 8, 1953 J. E. HAMMARSTROM 2,651,341

BOW SAW Filed May 11, 1951 2 Sheets-Sheet 2 Patented Sept. 8, 1953 Johan Evert Hammars assignor to Sandvik Sandviken, Sweden triim, Sandviken, Sweden, ens Jernverks Aktieholag,

Application May 11, 1951, Serial No. 225,719

Sweden March 15, 1949 3 Claims. ((1145-33) T The present invention relates to the type of saws which are called bow saws.

Such saws nowadays usually consist of bent steel tubes between the ends of which a saw blade is resiliently tensioned by means of a tensioning or lockingdevice. In order to facilitate special sawing operations it has been proposed to provide the bow saws with a handle situated under the saw blade and secured to either one of the bow ends. However, this handle may be an obstacle, e. g. when a log lying on the ground is to be sawn in two, because the handle is likely to strike the ground before the work is finished. With a view to obviating this disadvantage saws with detachable handles have been proposed. However, these saws are also attended with drawbacks consisting in that the detachable handles are likely to work loose. Further, it happens readily that an occasionally detached handle is lost.

The principal object of the present invention is to eliminate the above-mentioned drawbacks by providing a bow or frame a portion of which has the form of a part of a circle in the centre of which is situated a point of attachment for one end of a saw blade. The said portion forms one end portion of the bow while the centre of the circle lies at the other end portion of the bow, wherebv the other end of the saw blade which is connected to a tensioning and fixing device adiustable along the arched portion may be fixed in arbitrary positions along this portion. It is thus possible to place the tensioning device in such positions that the saw has a handle under the saw blade or has not. In the last-mentioned case the height of the bow is considerably greater than in the first-mentioned case.

The invention is more fully described in the following specification and illustrated in the accompanying drawings, in which:

Fig. 1 is a side view of a bow saw according to the invention.

Fig. 2 is another side view of the bow saw illustrating the saw blade placed in another position relative to the bow.

Fig. 3 is a fragmentary view of a tensioning device seen in the direction indicated by the arrow A in Fig. 1.

Fig. 4 is a fragmentary view, seen from below, of a tensioning device of another embodiment of the invention, and

Fig. 5 is a view of a tensioning device with a tensioning lever having the form of a separate handle.

Like parts are generally designated with like reference numbers in the figures.

In Fig. 1 the reference numbers I and 2 designate a bow and a saw blade respectively of a bow saw. The saw blade is at 3 pivotally connected to one end of the bow and at 4 likewise pivotally connected to members 5 of a tensioning device. The cross-section of the bow l is suitably that of a tube and preferably oval, in order to give the required stiiiness. The members 5, situated on both sides of the bow I, are by means of a bolt 6 pivotally connected to a tensioning lever I of an eccentric type which in the position shown retains the saw blade 2 firmly tensioned in the bow I. The friction between the tensioning device and the bow prevents the tensioning device from gliding along the bow. A projection 8 on the lever 1 serves to lock the lever and thus the whole tensioning device in the position in which the bow and the saw are under tension. The lever 1 has a form which, as will be apparent from Fig. 3, in the locking position corresponds to and partly embraces the tube I. The lever is further provided with a proiection 9 wh ch facilitates its operation when the tensioning device is to be released.

According to the invention the arched end portion 10 of the saw how has the form of a p rt of a circle whose centre is situated at the po nt of attachment of one end of the saw blade. Hereby it is possible to adiust the tension n device along the portion i0 and fix it in arhitrarv positions. Such a position is illustrated in Fi 2, and it will be understood that the part ii of th ortion in may be used as a handle. In the pos t on shown the saw blade is substantially parallel to the str ight middle portion of the bow.

Since the bow l alwavs settles somewhat when the saw blade is being tensiooed the po tion In mav advanta eouslv have such a form that the distance between the point of att hm nt 3 of the saw blade and the outmost end H of the portion Ill is sli htlv lon er than the distance betwe n the said point and the inner part of the portion.

In the embodiment shown n Fi 4 slots l3 are formed in the porti n In Throu h the s ts extends a saw blade, [4 whinh at, i5 is m'votallv connected to a slotted eccentric tensioning device '8 of a tvpe similar to that described in connection with Fi s. l-3. The slots in the portion I0 have a len th which is sufficient in or er to allow anv desired len th of the handle. The slots of the Dm't nn it! mav be closed or open.

As will be clear from Fig. 5 the lever of the tensioning device may form a separate handle Hi. In order to prevent accidental release of the tensioning device due to any force executed on the handle 16 during the sawing operation a, locking ring H or the like may be placed on the bow and the end of the handle so as to lock the handle tO'EthQbOW.

In various embodiments the side of the bow on which the lever 1 is adapted to press may be flattened or provided with serrations or the like; in order to obtain firm engagement with corresponding projections formed on the tensioningdevice.

It is to be understood that the;invention-; is. not limited to the embodiments described and shown here since other embodiments,areopossible, within the scope of the appending claims,

Having now described my invention, what'I' claim as new and desire to secure by Letters-Bat ent is:

l; Inga bow saw, the: combination; comprising a bow, means at oneend of=s,aid=bow=-for.pivotally anchoring one, end of a, saw blade, theother end: of said bow including an arcuate portion having, a center of curvature located substa-ns tially coincident \vithrthe pivot axis' for theeblade at the opposite end, and an eccentrically-acting tensioning ancl locking device for securing the other end of said sawblade against said bow, the eccentric member: of said deviceincludinga handle; portion and an eccentric portion operated thereby and engageable with the outer face of said arcuate portion to effect the locking action and being adjustable therealong so as to enable fixing of the saw blade at different angular positions relative to said bow.

2. A bow saw as defined in claim 1 wherein the handleqportionrofrsaid eccentricJnember includes atoe portion adapted tolie: against theisurface of said bow and which further includes a ring surrounding and slidable along said bow over said toe portion for locking said eccentric member against accidental displacement.

bow saw as,- defined in claim 1 wherein the; arcuateportion of said how merges with a pQrt-idnrof2 progressively increasing radius in the direction of the bow end.

JOHAN: EVERT HAMMARS'IRDM.

References Cited in the file of this patent UNITED STATES PATENTS 

